<template>
    <div class="upload-excel">
        <div class="btn-upload">
            <el-button
                :loading="loading"
                size="mini"
                type="primary"
                @click="handleUpload"
            >
                点击上传
            </el-button>
        </div>

        <input
            ref="excel-upload-input"
            class="excel-upload-input"
            type="file"
            accept=".xlsx, .xls"
            @change="handleClick"
        />
        <div
            class="drop"
            @drop="handleDrop"
            @dragover="handleDragover"
            @dragenter="handleDragover"
        >
            <i class="el-icon-upload"></i>
            <span>将文件拖到此处</span>
        </div>
    </div>
</template>

<script>
import XLSX from 'xlsx';

export default {
    props: {
        beforeUpload: Function,
        onSuccess: Function,
    },
    data() {
        return {
            loading: false,
            excelData: {
                header: null,
                results: null,
            },
        };
    },
    methods: {
        generateData({ header, results }) {
            this.excelData.header = header;
            this.excelData.results = results;
            this.onSuccess && this.onSuccess(this.excelData);
        },
        handleDrop(e) {
            e.stopPropagation();
            e.preventDefault();
            if (this.loading) return;
            const files = e.dataTransfer.files;
            if (files.length !== 1) {
                this.$message.error('Only support uploading one file!');
                return;
            }
            const rawFile = files[0]; // only use files[0]
            if (!this.isExcel(rawFile)) {
                this.$message.error('Only supports upload .xlsx, .xls, .csv suffix files');
                return false;
            }
            this.upload(rawFile);
            e.stopPropagation();
            e.preventDefault();
        },
        handleDragover(e) {
            e.stopPropagation();
            e.preventDefault();
            e.dataTransfer.dropEffect = 'copy';
        },
        handleUpload() {
            this.$refs['excel-upload-input'].click();
        },
        handleClick(e) {
            const files = e.target.files;
            const rawFile = files[0]; // only use files[0]
            if (!rawFile) return;
            this.upload(rawFile);
        },
        upload(rawFile) {
            this.$refs['excel-upload-input'].value = null; // fix can't select the same excel
            if (!this.beforeUpload) {
                this.readerData(rawFile);
                return;
            }
            const before = this.beforeUpload(rawFile);
            if (before) {
                this.readerData(rawFile);
            }
        },
        readerData(rawFile) {
            this.loading = true;
            return new Promise((resolve, reject) => {
                const reader = new FileReader();
                reader.onload = e => {
                    const data = e.target.result;
                    const workbook = XLSX.read(data, { type: 'array' });
                    const firstSheetName = workbook.SheetNames[0];
                    const worksheet = workbook.Sheets[firstSheetName];
                    const header = this.getHeaderRow(worksheet);
                    const results = XLSX.utils.sheet_to_json(worksheet);
                    this.generateData({ header, results });
                    this.loading = false;
                    resolve();
                };
                reader.readAsArrayBuffer(rawFile);
            });
        },
        getHeaderRow(sheet) {
            const headers = [];
            const range = XLSX.utils.decode_range(sheet['!ref']);
            let C;
            const R = range.s.r;
            /* start in the first row */
            for (C = range.s.c; C <= range.e.c; ++C) { /* walk every column in the range */
                const cell = sheet[XLSX.utils.encode_cell({ c: C, r: R })];
                /* find the cell in the first row */
                let hdr = 'UNKNOWN ' + C; // <-- replace with your desired default
                if (cell && cell.t) hdr = XLSX.utils.format_cell(cell);
                headers.push(hdr);
            }
            return headers;
        },
        isExcel(file) {
            return /\.(xlsx|xls|csv)$/.test(file.name);
        },
    },
};
</script>

<style scoped lang="scss">
.upload-excel {
  display: flex;
  justify-content: center;
   margin-top: 100px;
   .excel-upload-input{
       display: none;
        z-index: -9999;
     }
   .btn-upload , .drop{
      border: 1px dashed #bbb;
      width: 350px;
      height: 160px;
      text-align: center;
      line-height: 160px;
   }
   .drop{
       line-height: 80px;
       color: #bbb;
      i {
        font-size: 60px;
        display: block;
      }
   }
}
</style>
